23
MAR
2016

NPA 2016-01

Helicopter ditching and water impact occupant survivability

This Notice of Proposed Amendment (NPA) addresses safety issues related to helicopters certified for ditching and performing overwater operations.

Previous studies on and accident investigations into helicopter ditchings and water impact events have highlighted inadequacies in the existing certification specifications (CS-27, CS-29) and in the rules governing offshore operations. In particular, it has been established that in an otherwise survivable water impact, most fatalities occurred as a result of drowning because the occupants were unable either to rapidly escape from a capsized and flooded cabin, or to survive in the sea for sufficient time until rescue. Furthermore, the testing environment in which helicopters are type-certified for ditching bears little resemblance to the sea conditions experienced in operation.

In order to thoroughly address these and other ditching-related issues, and due to the nature of ditching-related hazards, this rulemaking task (RMT.0120 (27&29.008)) has taken a holistic approach to the problem, which crosses traditional airworthiness/operational boundaries. A detailed risk assessment has been undertaken that reflects both certification and operational experience and builds upon data extracted from accident reports and previous studies. The result is a list of identified interventions related to helicopter design, certification, operations, and ditching equipment, all of which could contribute to improving safety. In the case of operations, the Rulemaking Group (RMG) RMT.0120 (27&29.008)) has interfaced with the RMG RMT.0409 & RMT.0410 (OPS.093(a)&(b)), amending Annex V (Part-SPA) to Regulation (EU) No 965/2012 to introduce helicopter offshore operations (HOFO), to ensure a consistent set of rules.

The specific objective of this NPA, however, is to propose changes to CS-27 and CS-29 to mitigate helicopter design-related risks to new helicopter types. Recommendations for safety improvements in other areas have been made by the RMG for subsequent action to be taken under this rulemaking task, other rulemaking tasks or through alternative means. Retroactive rules are to be considered in a second phase of this RMT.

This NPA proposes changes to many CS-27/29 provisions that relate to ditching. However, the primary change proposed aims to establish a new ditching certification methodology by which a target probability of capsize following a ditching can be determined based on the level of capsize mitigation applied to the design. This target probability of capsize is then verified in sea conditions chosen by the applicant, by following a defined tank test specification using irregular waves. For CS-29 and CS-27 Cat A rotorcraft, enhanced capsize mitigation must be provided to relieve the time pressure on occupants to escape. Water impact events are accounted for implicitly within the new ditching methodology. Additional changes are proposed to maximise the likelihood of occupant egress and subsequent survivability.

The proposed changes are expected to increase safety.

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